A standard drill chuck has a chuck body that is mounted on the spindle or arbor of a drill power unit or other similar machine and that is provided externally with a so-called tightening sleeve. A plurality of angularly equispaced jaws are provided between this sleeve, and the chuck body is provided with formations that can move these jaws radially toward each other or radially apart on relative rotation of the tightening sleeve and the chuck body. Normally the jaws are spring-loaded radially outwardly. They are moved radially inwardly when the tightening sleeve is rotated relative to the chuck body by being pushed forward on an inner frustoconical surface of the tightening sleeve.
In order to prevent such a chuck from loosening it is known to provide a ratchet arrangement that normally only allows the tightening sleeve to rotate in the tightening direction on the chuck body. A ratchet pawl is pivotal about an axis parallel to the chuck axis on a special holding ring clamped to the chuck body. Teeth are formed on the so-called pressure ring that is threaded to the tightening sleeve and that serves to axially fix the tightening sleeve relative to the chuck body. This pawl has a button projecting radially out of the holding ring through a window formed therein and is not only spring loaded into position with its end engaged in the teeth of the pressure ring, but is also so counterbalanced that radially outwardly effective centrifugal force will increase the radial inward force of its tooth into the teeth of the pressure ring.
An improvement on such an arrangement is described in U.S. Pat. No. 4,302,021. It has a ratchet pawl carried on the pressure ring that is fixed to the tightening sleeve. A release ring is provided which is angularly displaceable on the chuck between a holding position which allows the tension spring of the ratchet pawl to press the end of the pawl against the teeth and a releasing position holding the end of the pawl out of engagement with these teeth.
Such a chuck works very well, but is often somewhat long, measured parallel to its axis. Thus the drill itself presents itself as a fairly long and bulky tool, largely because of the length of the chuck.